Synthetic lubricants



- SYNTHETIC LUBRIGANT S Bernard A- Orkin, PhiladelphimPa .assignortoSocony- Vacuum Oil Company,.lncorporated, a corporation of New York NoDrawing. Application October 20, 1948, Serial No. 55,639

4 .Claims. (Cl. 260-93323) I: This invention relates, broadly, toester-type synthetic lubricants having a combination of desirableproperties,

namely, high viscosity indices, relatively low pour' points,goodstability,-and increased resistance to hydrolys1s, 'an'd it is moreparticularly concerned with certain silicate .estershaving theaforementioned combination of desirabl'e properties.

The silicate esters contemplatedherein' are organic compounds having theformula, RnSi(TR-')4-1t, wherein R:.and R- are'aliphatic, alicyclic,aryl, aralkyl, or heterocyclic'radicals; Tv represents an oxygen or asulfur three.

The preparationv of'compounds having the general formula,1R1iSi(.OR)4-n, haszbeen described by Cusa and Kipping (J. Chem. Soc.,1933;1-040); by Griitner and Cauer [Ber., 51, 1283 (1918)]; by Kipping(J. Chem. Soc., 1927, 1228'); and by Postand Hofrichter [J. Org. Chem.,,5,572 (1940)]. However, the products. described in the literature havehad verylow'viscosities. This destroys their utility as lubricants. .Anumber of esters of silicic acid are-known to display unusual stabilitytoward heatand oxidation. .Thus, tetracresyl' .silicate, which has beenwidely used as a heat transfermcdium, can be heated to about 450?C.withoutperceptible decomposition. Such esters, however, possess.disadvantageous properties in that they readily undergo" hydrolysis inthe presence of 'water at elevated temperatures. By reducing the numberof. .alkoxy groups in the molecule, i. e., by creating one or moredirect carbonsilicon=linkages, and by increasing the total" number ofsatomg'and n is. an integer varying between one and 2,701,803 PatentedFeb. 8, 1955 2 readily byreacting axcompoundhaving the formula,RnSiX4-n, wherein-R is an aliphatic, an alicyclic, an aryl, an-,aralkyl, or .a heterocyclic radical; X is a halogen atom;.and.n.is an:integer varying between one and three,

with a compound havingthe-formula, RTH, wherein R I is. an aliphatic, an.alicyclic, anaryl, an aralkyl, or a heterocyclic radical, and Tis anoxygen or a sulfunatom, innaccordance with the following equation:

prepare the products of the present invention 1 are prepared bythereaction betweena silicon tetrahalideand a. suitable Grignardreagent. .The preparation is set forth in the following equation:

wherein R is'an aliphatic, an .alicyclic, an aryl, anaralkyl, or aheterocyclic radical, and X is a halogen; atom. These procedures havebeen amply described by-Kipping, Murray, and Maltby (J ."Chemi Soc.,1929, 1180), Hyde and De Long. [.l.,-Am.-Chem. Soc., 63, 1194 (1941)],and Gilliam, Liebhafsky, and-Winslow [J. AmaChem. Soc., 63, 801 (1941)].-The pure reactant having. the formula RnsiXr-n isisolated and purifiedby conventional operations, such as fractional distillation orcrystallization.

It "iswithin the'concept of this invention to utilize mixturesof-sthis.reactant withoutpurification, inprecarbon atoms inthe molecule,an ester -is obtained which is much less miscible i'with water'and,accordingly, is less prone tov undergo hydrolysis in the presence ofwater, even at elevated temperatures; The compounds having the generalformula, 'Rn'Si(SR)4-n, have never been described in theliterature,sin=so far as is now known.

been. discovered that. esters having-rthe formula, RaSi(TR')4 a, whereinR, R, T,:-and"n-v are as :defined hereinbefore and' having' betweenabout 24 and about 40 carbon and heterocyclic-atoms per molecule,possess a combination of all of the desirable properties mentionedhereinbefore. It has now been found that esters having the formula,RnSi(TR')4 .n, can be. prepared in good'yields and in a simple ande'fiicientmanner.

Accordingly, it is a broad object'of the present-invention to providenew compositions of matter.: Another object is'to provide a new class of.silicate esters.. An important object is to provide silicate ester-typeof. synthetic lubricants having high viscosity-indices, relatively lowpour points, good stability, and increased resistance to is an integervarying between one andthree; in which the tOtaL'number of. carbonatomsand heterocyclic atoms in each molecule varies between-about 24-andabout 40, and;.preferably, betweenabout 26 and-about 38.

.The-esters of the present invention can 8 beprepared Other objectsandadvantages of the pres- 1 are available in commercial quantities.

, thiol, thienylthiol-3, 2-ethylthienylthiol-3, and pyridylthibl-Z,

paring compoundsof: the type contemplated herein. Obviously, suchcompounds will'not be pure,-but they will be mixtures-which,nevertheless, afford excellent synthe tic;- lubricants.

The alcohol orphenolreactants characterized by the formula, RTH, setforthhereinbefore, which are used to prepare the synthetic lubricantsofthe present invention are themonohydroxy aliphatic alcohols,-alicyclicalcohols, phenols, aromatic alcohols, and heterocyclic alcohols.Non-limiting examples are propanol-l, -butanol-l, Z-methyl. propanol-l,pentanol-l, hexanol-l, 2- ethylhexanol l; octanol-ly-octanol-2,dodecanol-l, octadecanol-1, cyclohexanol, v-2,-methylcyclohexanol,'3-meth- .ylcyclohexanol phenol, Z-methylphenol; 3-methylphenol,4-methylphenol, -benzyl alcohol, a-naphthol, fi-naphthol, Zhydroxy 5.methylthiophene, 3-hydroxy-5-phenyl thiophene,- Z-hydroxypyridine,-v3-hydroxypyridine, and 8- hydroxyquinoline. The preparation of thesematerials is set-forth in the literature and many of them are availablein commercial uantitiesn While it will be --a In accordance with thepresent invention, it has* now q p parentthat the alcohol or phenolreactants should be pure in order tohobtain products of.reasonablepurity, it -is- .withinthe .scope of the. present inventionto=-use technical. grade alcohols orrphenols, mixtures containing .1,alcohols orphenols, -or-mixturestof two (or more .alcohols'and/orphenols; ltwilltbe readily. understoodwthat productsamade fromsuchmixtures willrnot be pure-compounds. However, they have been foundtobe excellent syntheticrlubricants intaccordance with the presentinvention.

.The' thiol-reactants,- characterized by the aforementioned formula,RTH,:utilizable-herein includethe alkanethiols and the cyclic thiols, i.e., cycloalkanethiols, aranethiols, and heterocyclic thiols.Propanethiol-l, butanethiol-l, 2-methylpropanethiol-l, pentanethiol-l,2- methylbutanethiol-4, hexanethiol-l, octanethiol-l, 2-ethylhexanethiol-l, decanethiol-l,.dodecanethiol-l, cyclopentanethiol,cyclohexanethiol, methylcyclohexanethiols, thiophenol, o-tolylthiol,m-tolylthiol, p-tolylthiol, benzyl a-naphthylthiol, fit-naphthylthiol,thienylthiol-Z,

may be mentioned by way of non-limiting examples.- The thiols may beprepared in many different ways, as is well known to those familiar withthe art, and many In order to obtain reasonably pure synthetic lubricantproducts, the thiol reactant should be pure. However, as those skilledin the art will readily appreciate, the thiol reactant may 0 beeftechnical grade,.a mixture containing thiol reactants,

or a mixture oftwoor more thiol reactants; Obviously,

products made from such mixtures or impure reactants will not be purecompounds. Nevertheless, they have been found to be satisfactorysynthetic lubricants, within the scope of the present invention.

An excess of the reactant having the formula, RTH, over that required toreact with all of the halogen atoms in the compound having the formula,RnSlX4-1r, as indicated in Equation 1 set forth hereinbefore, must beused. Ordinarily, as many as four moles of the reactant having theformula, RTH, for each halogen atom in the compound having the formula,RnSiX4-n is used. In practice, the mole ratio of the reactant having theformula, RTH, to the reactant having the formula, RnSiXi-n, may varybetween about two to one and about twelve to one, respectively.

As set forth hereinbefore, the sum of the number of carbon atoms andheterocyclic atoms in the compounds having the formula RnSi(TR')4-n,varies between about 24 and about 40 and, preferably, between about 26and about 38. This requirement will be the only limiting factor as tothe number of carbon and heterocyclic atoms in the reactant having theformula, RTH. For example, if the reactant, RnSIX4n, istrihexylchlorosilane, the reactant having the formula, RTH, must containno fewer than six, nor more than twenty-two carbon and heterocyclicatoms per molecule.

For practical reasons, it is preferable to carry out the reaction in anon-polar hydrocarbon solvent. Especially preferred are the aromatichydrocarbon solvents such as, for example, benzene, toluene, and xylene.The amount of solvent to be used will vary between about 25 per cent andabout 90 per cent by weight, based on the total weight of the reactants.

The temperature of the reaction is not too critical a factor. Ingeneral, the temperature will be the reflux temperature of the solventused and, preferably, it varies between about 80 C. and about 140 C. Thetime of reaction will depend on the temperature employed. In practice,the reaction is complete after heating the reactants at the preferredtemperatures for a period of time varying between about 2 hours andabout hours, after all reactants have been added.

The reactant having the formula, R'SH. is reacted with the reactanthaving the formula, RnSlX4n, in the presence of a trialkylamine. Theamine combines with the hydro en halide evolved during the reaction toform an insoluble amine hydrohalide which is subsequently removed byconventional methods of separation, such as filtration or decantation.Amines utilizable for this purpose are the trialkyl amines havingbetween one and three carbon atoms per alkyl radical. Non-limitingexamples are triethylamine and tripropylamine. At least one mole ofamine should be used for each halogen atom in the compound having theformula, RnSiX4-n. In practice, the ratio of amine reactant to thereactant having the formula, RnSlX4-7t, may vary between about one toone and about twelve to one, respectively.

The desired reaction product is isolated by distilling oif, under normalor reduced pressure, excess solvent, amine, reactant having the formulaR'TH and any unreacted RnSlX4n reactant. The desired ester is recovered.in relatively pure form, as the residue from the distillation operation.

It will be apparent to those skilled in the art that the esters of thepresent invention may be prepared in ways other than that set forthhereinbefore. For example, a compound having the formula, (R'T)4nsiXn,may be prepared by reacting a compound of the formula, RTH, with asilicon tetrahalide and fractionating the resulting reaction mixture.This reactant,

is then reacted with the Grignard reagent to form the product having theformula, RnSi(TR')4-1L, in accordance with the following equation:

R'T) 4nSlXn+ nRMgX- RnSi TR 4-n+nMgXz The conditions and techniques forpreparing compounds having the formula, (RT)47LSiX7Z, are set forth in a80 copending application, Serial Number 42,535, filed by Orkin on August4, 1948. The techniques involved in preparing the Grignard reagent arewell known to those skilled in the art. Accordingly, they will not bediscussed in detail herein. The ester products prepared in this mannerare isolated by procedures similar to those set forth hereinbefore.

The following specific examples are for the purpose of exemplifying theesters of the present invention. It is to be clearly understood,however, that the invention is not to be considered as limited to thespecific reactants used, or to the operations and manipulationsdescribed in the examples. As will be apparent to those skilled in theart, other reactants, as set forth hereinbefore, may be used to preparea wide variety of products in accordance with this invention.

EXAMPLE 1 Trioctylphenoxysilane The Grignard reagent was prepared in theconventional manner from 81.5 grams of n-octyl bromide and 11.8 grams ofmagnesium in the presence of 170 cubic centimeters of absolute diethylether. To this reagent were added 22 grams of phenoxytrichlorosilane in50 cubic centimeters of absolute diethyl ether, and the solution wasrefluxed for 2.5 hours. Then, the excess Grignard reagent was destroyedthrough the addition of ice water and dilute sulfuric acid. The etherlayer was separated, and the aqueous layer was extracted with ether. Theextracts were combined with the main portion of the ether solution. Thecombined ether solutions were then dried and distilled to remove theether. The distillation was continued up to a pot temperature of about250 C., under a pressure of five millimeters to remove all volatilematerials. The residue, after filtering through clay, consisted of 22grams of a clear liquid. Pertinent data are set forth in Table I.

EXAMPLE 2 Diethyldi(0ctoxy) silane To a warm solution of 58 grams ofdiethyldichlorosilane in 200 cubic centimeters of xylene, there wereadded, dropwise, 104 grams of octanol-l. The solution was held at refluxtemperature (about 135 C.) for about four hours and then topped at 250C., under two millimeters pressure. The residue was filtered and itconsisted of 1135 grams of a clear, mobile fluid having the propertiesset forth in Table I.

EXAMPLE 3 Phenyltri dodecoxy silane A mixture of 29 grams ofphenyltrichlorosilane, 93 grams of dodecanol-l, and 80 grams of benzenewere heated at reflux temperature (about 80 C.) until evolution ofhydrogen chloride had ceased (about three hours). More volatilematerials were distilled out at atmospheric temperature, and the excessdodecanol-l was removed at C., under a pressure of three millimeters.The residue, after filtration, was a clear, slightly viscous oilcontaining 4.55 per cent silicon (C42H8003Si contains 4.25 per centsilicon) and weighing 70 grams. Pertinent properties are given in TableI.

EXAMPLE 4 Benzyltri(0ctylthio silane A solution of 13 grams ofbenzyltrichlorosilane and 43 grams of octanethiol-l in 200 cubiccentimeters of benzene was placed in a reaction vessel. To this solutionwas added, dropwise, 37 grams of triethylamine. After the addition wascomplete, the reaction mixture was heated at reflux temperature (about80 C.) for four hours. The reaction mixture was then filtered and thetriethylamine hydrochloride was washed with benzene. The filtrate wastopped free of benzene and unreacted materials at about C. under about 2millimeters pressure. The residue was filtered through filtering clay.The product was a yellow, oily material havmg properties as set forth inTable I.

EXAMPLE 5 Thienyltri(decylthio)silane To a solution of 21.8 grams ofthienyltrichlorosilane and 69.6 grams of decanethiol-l in 300 cubiccentimeters of xylene, there were added 40 grams of triethylamine. Theresultant reaction mixture was heated at the reflux temperature (aboutC.) for about 2 hours. The reaction product was filtered to removetriethylamine hydrochloride and the filtrate Was topped to remove thelow-boiling materials. The resultant product, after filtering throughfiltering clay, consisted of 33.5 grams of an orange, mobile liquid. Thepertinent physical properties are set forth in Table 1.

EXAMPLE 6 Diethyldi(decylthi0)silane To 24 grams ofdiethyldichlorosilane and 58 grams of decanethiol-l in 200 cubiccentimeters of xylene were added gradually 67 grams of triethylamine.-After the addition was complete, the mixture was refluxed at 135 C. forabout 3 hours, then cooled and filtered. The filtrate was topped at 200C. under about millimeters pressure and the residue was filtered throughfiltering clay. The physical data for the light yellow, mobile liquidproduct are set forth in Table I.

It will be apparent, from the data set forth in Table I, that theproducts having the formula, RnSi(TR')4-n, in which the total number ofcarbon atoms and heterocyclic atoms varies between about 24 and about40, are excellent synthetic lubricants having high viscosity indices,relatively low pour points, and good stability. The criticalness of theminimum number of carbon and heterocyclic atoms is demonstrated by thedata for the product of Example 2 having atoms per molecule, wherein theviscosity is so low that the product has no utility as a lubricant. Onthe other hand, the product of Example 3, having 42 carbon atoms permolecule, has an undesirably high pour point.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be resorted to without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand. Suchvariations and modifications are considered to be Within the purview andscope of the appended claims.

What is claimed is:

1. Trioctylphenoxysilane.

2. Benzyltri(octylthio)silane.

3. Thienyltri(decylthio)silane.

4. A compound having the formula RnSi(TR')4-n, wherein R and R areradicals selected from the group consisting of alkyl, thienyl and benzylradicals, T is a divalent atom selected from the group consisting ofoxygen and sulfur atoms, and n is an integer varying between one andthree, in which the total number of carbon atoms plus heterocyclic atomsin each molecule varies between 26 atoms and 38 atoms, there being notmore than 3 heterocyclic atoms per molecule, and in which at least oneof said radicals R and R is an alkyl radical; said compound being alubricant having a relatively low pour point, a high viscosity index, aviscosity in the lubricating oil range, and resistance to hydrolysis.

References Cited in the file of this patent UNITED STATES PATENTS2,129,281 Lincoln Sept. 6, 1938 2,386,452 Fleming Oct. 9, 1945 2,386,793Hanford Oct. 16, 1945 2,397,727 Daudt Apr. 2, 1946 2,439,689 Hyde Apr.13, 1948 2,462,267 Hyde Feb. 22, 1949 2,527,233 Sowa Oct. 24, 19502,562,474 Orkin et al. July 31, 1951 OTHER REFERENCES Chemical Abstracts35, 2470, item 3 (1941). Cusa, J. Chem. Soc. 136, 1040-3 (1933).NwYhitnilggel, Organic Chemistry, p. 884, Van Nostrand,

4. A COMPOUND HAVING THE FORMULA RNSI(TR'')4-N, WHEREIN R AND R'' ARERADICALS SELECTED FROM THE GROUP CONSISTING OF ALKYL, THIENYL AND BENZYLRADICALS, T IS A DIVALENT ATOMS SELECTED FROM THE GROUP CONSISTING OFOXYGEN AND SULFUR ATOMS, AND N IS AN IONTEGER VARYING BETWEEN ONE ANDTHREE, IN WHICH THE TOTAL NUMBER OF CARBON ATOMS PULS HETEROCYCLIC ATOMSIN EACH MOLECULE VARIES BETWEEN 26 ATOMS AND 38 ATOMS, THERE BEING NOTMORE THAN 3 HETEROCYCLIC ATOMS PER MOLECULE, AND IN WHICH AT LEAST ONEOF SAID RADICALS R AND R'' IS AN ALKYL RADICAL; SAID COMPOUND BEING ALUBRICANT HAVING R RELATIVELY LOW POUR POINT A HIGH VISOCITY INDEX, AVISOCITY IN THE LUBRICATING OIL RANGE, AND RESISTANCE TO HYDROLYSIS.